THE conversation I've had with so many friends goes something like this:

"I'm worried because if Obama gets the nomination, he can't possibly win, and we'll be stuck with McCain."

Or, "I sure hope Hillary doesn't somehow get the nomination because there's no way she can win, and then we'll get McCain."

Or even, with some Republican friends (and yes, I do have a few), "I don't think there's any way McCain can win."

How can this possibly be?

One idea is that Barack Obama can't win because too many white Americans are fundamentally racist, and no matter what they tell themselves or pollsters, they aren't ready to vote for a black man. And Democrats can't win without them.

That's certainly Hillary Clinton's theory when she says she, not he, should be the nominee because she has the support of "hardworking Americans, white Americans." And it's been true, according to pollsters, that white Democrats with less income and less education have been more likely to vote for Clinton than for Obama.

And Obama hasn't done particularly well among Latino or Asian voters, either.

Women supporting Hillary will be so disappointed at a loss by the most viable female candidate for president ever that even if they are Democrats, many may stay home, or vote for John McCain.

Plus there's still a percentage of the electorate who believe that Obama is a secret Muslim sent to take over the country, or somehow related to Osama bin Laden, or Saddam Hussein.

Add all these together - and Obama can't possibly win.

On the other hand, Obama's supporters argue that Hillary can't win. Her negatives are so high, and many conservative Republicans hate her so much that even those not especially enthusiastic about McCain will come out in droves to vote against her. Anti-Hillary sentiment will boost fundraising for the Republicans, who've been lagging far behind the Democrats in this contest.

She can't get the new voters who've plunged into the electoral process because of Obama's promise of change in Washington. They'll drop out if she gets the nomination. And there are many voters who are just tired of the Clintons and don't want to see them back in the White House.

Finally, Obama's black supporters will be furious that their guy played by the rules and won the nomination fair and square, only to have it snatched away. They won't vote for the white woman who attacked him, and in many places, Democrats just can't win without the overwhelming support of the black electorate.

Add all these together, and Hillary can't win in November.

These are the Democratic nightmares. What about the GOP?

Look at the three recent special elections to fill seats in Congress that were all won by Democrats, even in heavily Republican districts. "They are canaries in the coal mine, warning of far greater losses in the fall," said a prominent GOP congressman.

Republicans know that President Bush is an albatross around the neck of McCain. That the vast majority of Americans think the country is going in the wrong direction. That the Democrats are already saying that McCain is running for George Bush's third term.

They fear that their candidate's age, his famous temper and wife Cindy McCain's financial ties may pose additional problems. No, McCain can't possibly win.

Except, one of them will.

One of these theories will be proven wrong, since someone has to be sworn in as our next president. But which one? Your guess is as good as mine. *

Deborah Leavy is a regular contributor to the op-ed page and an associate member of the Daily News editorial board. E-mail her at deborah.opinion@gmail.com.